This invention relates generally to computer-based methods and system for designing products, and more particularly to a computer-based method and system for designing a low pressure turbine shaft.
An aircraft gas turbine engine generally comprises a compression section, a burner section and a turbine section. Each section operates on the working fluid in a well-known manner to generate thrust. The compression section may include a fan, a low pressure compressor and a high pressure compressor. The turbine section may include a low pressure turbine and a high pressure turbine. The low pressure turbine is coupled to a low pressure turbine shaft for driving the fan.
The low pressure turbine shaft is a cylindrically shaped gas turbine engine component which is coupled to the low pressure turbine in one end of the gas turbine engine and extends within the gas turbine engine to the fan located in the air inlet section of the engine. The low pressure turbine shaft is designed to physically and operationally accommodate the surrounding components, such as the compressors, the burners and the turbines. The design of the low pressure turbine shaft must provide space, or clearance, for the other gas turbine engine components during both assembly and operation while meeting performance, weight and durability requirements.
In addition, elements such as an aft-hub and a stub-shaft may be joined to the low pressure turbine shaft. Both the elements and the means of joining must also meet the performance, the weight and the durability requirements.
It is known to design various products using a computer-aided design (xe2x80x9cCADxe2x80x9d) system, a computer-aided manufacturing (xe2x80x9cCAMxe2x80x9d) system, and/or a computer-aided engineering (xe2x80x9cCAExe2x80x9d) system. For sake of convenience, each of these similar types of systems is referred to hereinafter as a CAD system. A CAD system is a computer-based product design system implemented in software executing on a workstation. A CAD system allows the user to develop a product design or definition through development of a corresponding product model. The model is then typically used throughout the product development and manufacturing process. An example is the popular Unigraphics system commercially available from Unigraphics Solutions, Inc. (hereinafter xe2x80x9cUnigraphicsxe2x80x9d).
In addition to CAD systems, there is another type of computer-based product design system which is known as a xe2x80x9cKnowledge-Based Engineeringxe2x80x9d(xe2x80x9cKBExe2x80x9d) system. A KBE system is a software tool that enables an organization to develop product model software, typically object-oriented, that can automate engineering definitions of products. The KBE system product model requires a set of engineering rules related to design and manufacturing, a thorough description of all relevant possible product configurations, and a product definition consisting of geometric and non-geometric parameters which unambiguously define a product. An example is the popular ICAD system commercially available from Knowledge Technologies, Inc. KBE systems are a complement to, rather than a replacement for, CAD systems.
An ICAD-developed program is object-oriented in the sense that the overall product model is decomposed into its constituent components or features whose parameters are individually defined. The ICAD-developed programs harness the knowledge base of an organization""s resident experts in the form of design and manufacturing rules and best practices relating to the product to be designed. An ICAD product model software program facilitates rapid automated engineering product design, thereby allowing high quality products to get to market quicker.
The ICAD system allows the software engineer to develop product model software programs that create parametric, three-dimensional, geometric models of products to be manufactured. The software engineer utilizes a proprietary ICAD object-oriented programming language, which is based on the industry standard LISP language, to develop a product model software program that designs and manipulates desired geometric features of the product model. The product model software program enables the capturing of the engineering expertise of each product development discipline throughout the entire product design process. Included are not only the product geometry but also the product non-geometry, which includes product configuration, development processes, standard engineering methods and manufacturing rules. The resulting model configuration and parameter data, which typically satisfy the model design requirements, comprise the output of the product model software program. This output, from which the actual product may be manufactured, comprises a file containing data (e.g., dimensions) defining the various parameters and configuration features associated with each component or element of the product.
Also, the product model software program typically performs a xe2x80x9cwhat ifxe2x80x9danalysis on the model by allowing the user to change model configuration and/or parameter values and then assess the resulting product design. Other analyses (e.g., a weight analysis) may be run to assess various model features with regard to such functional characteristics as performance, durability and manufacturability. These characteristics generally relate to the manufacturing and operation of a product designed by the product model software program. They are typically defined in terms of boundaries or limits on the various physical parameters of each product feature. The limits have been developed over time based on knowledge accumulated through past design, manufacturing, performance, and durability experience. Essentially, these parameters comprise rules against which the proposed product model design is measured. The rules generally comprise numbers that define physical design limits or constraints for each physical product parameter. Use of these historically developed parameters, analyses, and design procedures in this way is typically referred to as product xe2x80x9crule-based designxe2x80x9d or xe2x80x9cknowledge-based designxe2x80x9d. The rules determine whether the resulting product design will satisfy the component design requirements and whether the design is manufacturable, given various modern manufacturing processes. The rules for a particular product design are pre-programmed into the product model software program for that specific product.
While the ICAD system provides an excellent tool for developing software product models, it is not a replacement for an organization""s primary CAD system, which maintains the product model definition throughout the entire product design and manufacturing cycle. This is because the ICAD system is a KBE software development tool rather than a CAD system. For example, while the ICAD system can create a geometric model, it cannot easily create drawings based on that model or support other aspects of the design process typically provided by CAD systems. As such, for the product model created in the ICAD system to be useful throughout the entire product development process, the model must be translated into a CAD system for further manipulation.
Another inherent problem with the commercial ICAD system is that the parametric model created by the product model software program cannot be transported as a similar parametric product model into a Unigraphics CAD system. Instead, the parametric model in ICAD must be transported into Unigraphics as a non-parametric model.
Since design and manufacturing technology is always evolving, the product model imported from the ICAD system into Unigraphics will usually be enhanced with new technology design or manufacturing features. Furthermore, since it is difficult to make modifications to a non-parametric model in Unigraphics, revisions to the product model must normally be made in the ICAD system and re-imported into Unigraphics. This causes any additional features previously added in Unigraphics to be lost.
On the other hand, the Unigraphics CAD system has inherent problems in that not all of the parametric models created by Unigraphics are xe2x80x9cstandardizedxe2x80x9dwithin an organization or industry. Also, parametric models implemented in Unigraphics do not effectively implement a KBE system (similar to the ICAD system) that requires the model configuration and order of Boolean operations to vary according to design requirements. Also, a Unigraphics parametric model cannot be structured to provide parameter relationships that satisfy both design and manufacturing requirements.
As a result, there are instances when a product model developed solely in either the ICAD system or the Unigraphics system will suffice, even with the aforementioned shortcomings. However, there are other instances when it is desired to transport a product model developed in the ICAD system to the Unigraphics CAD system even as a corresponding non-parametric product model.
An object of the present invention is to provide a computer-based method of creating a parametric, three-dimensional, geometric product model of the low pressure turbine shaft system of a gas turbine engine.
Another object of the present invention is to provide a computer-based method of creating a non-parametric product model in a KBE system that can be recreated as a similar product model in a CAD system.
The above and other objects and advantages of the present invention will become more readily apparent when the following description of a best mode embodiment of the present invention is read in conjunction with the accompanying drawings.
A method for designing a low pressure turbine shaft including the step of creating a low pressure turbine shaft knowledge base of information. The knowledge base has a plurality of design rule signals with respect to a corresponding plurality of parameter signals of associated elements of a low pressure turbine shaft, wherein the knowledge base comprises at least one data value signal for each one of the plurality of design signals. The method includes the steps of entering a desired data value signal for a selected one of the plurality of parameter signals of an associated element of the low pressure turbine shaft and comparing the entered desired data value signal for the selected one of the plurality of parameters with the corresponding at least one data value signal in the knowledge base for the corresponding one of the plurality of design rule signals. The method also includes creating signals representative of a geometric representation of the selected one of the plurality of parameter signals of the associated element of the low pressure turbine shaft if the result of the step of comparing is such that the entered desired data value signal for the selected one of the plurality of parameter signals is determined to have a first predetermined relationship with respect to the corresponding at least one data value signal in the knowledge base for the selected one of the plurality of design rule signals.
A computerized system for designing a low pressure turbine shaft comprises a low pressure turbine shaft knowledge base for storing a plurality of low pressure turbine shaft design parameter signals corresponding to a plurality of design rule signals for creating a geometric representation of a low pressure turbine shaft. The system also includes selection means for receiving a parameter value signal corresponding to at least one of the design parameter signals, and processing means for comparing the parameter value signal with the at least one of the design parameter signals stored in the knowledge base, and means for creating the geometric representation of the low pressure turbine shaft if the parameter value signal has a first predetermined relationship with the design parameter signal and at least one of the design rule signals.